Remelting of rare earth magnet scrap and/or sludge, magnet-forming alloy, and sintered rare earth magnet

Abstract

Rare earth magnet scrap and/or sludge is remelted for reuse. Once a rare earth-free magnet-constituent metal feed is loaded in a melting furnace and heated into a melt, a rare earth-containing metal feed and the rare earth magnet scrap and/or sludge are added to the melt, a particulate flux of an alkali metal, alkaline earth metal or rare earth metal halide and having an average particle size of 1–50 μm, preferably wrapped in a metal foil, is added to the melt, and the resulting mixture is melted, from which an alloy ingot is obtained. The valuable elements in the scrap and/or sludge can be recycled. Better separation between the slag and the molten metal ensures that the ingot is obtained from the melt in a high yield.

1. A process of preparing a sintered rare earth magnet comprising the steps of:
 charging a melting furnace crucible with a rare earth-free magnet-constituent metal feed; 
 heating the metal feed for melting into a melt; 
 adding to the melt a rare earth containing metal feed and 0.1 to 50% by weight based on the metal feeds of an R—Fe—B base rare earth magnet scrap and/or sludge wherein R is a rare earth element inclusive of yttrium; 
 further adding 0.01 to 30% by weight based on the metal feeds of a particulate flux containing a halide of at least one metal selected from among alkali metals, alkaline earth metals and rare earth metals and having an average particle size of 1 to 50 μm; 
 melting the resulting mixture; and 
 crushing, comminuting, compacting in a magnetic field, and sintering the resulting alloy. 
 
     
     
       2. The process at  claim 1 , wherein the step of heating the metal feed for melting into a melt is conducted at a temperature of 1500 to 1800° C. 
     
     
       3. The process of  claim 1 , wherein the step of melting the resulting mixture is conducted at a temperature of 1500 to 1800° C. 
     
     
       4. A process of preparing a sintered rare earth magnet comprising the steps of:
 charging a melting, rare earth-free magnet-constituent metal feed; 
 heating the metal feed for melting into a melt; 
 adding to the melt a rare earth-containing metal feed and 0.1 to 50% by weight based on the metal feeds of an R—Fe—B base rare earth magnet scrap and/or sludge wherein R is a rare earth element inclusive of yttrium; 
 wrapping a particulate flux containing a halide of at least one metal selected from among alkali metals, alkaline earth metals and rare earth metals and having an average particle size of 1 to 50 μm, within a magnet-constituent metal; 
 further adding 0.01 to 30% by weight based on the metal feeds of the metal wrapped flux; 
 melting the resulting mixture; and 
 crushing comminuting, compacting in a magnetic held, and sintering the resulting alloy. 
 
     
     
       5. The process of  claim 4 , wherein the step of heating the metal feed for melting into a melt is conducted at a temperature of 1500 to 1800° C. 
     
     
       6. The Process of  claim 4 , wherein the step of melting the resulting mixture is conducted at a temperature of 1500 to 1800° C.